Carrier 09DC - Manual (Page 3)

CONDENSER RATINGS TYPICAL ARRANGEMENTS
(Two-Module Condensers)
la. Select minimum or optimum charge ratings.
Use optimum charge when compressor, condenser, and
evaporator may be selected as a package and the com­
ponents may be balanced* to secure maximum benefits
of 15 F subcooling (for example, in selecting 09DC con­
densers with Carrier compressors rated at 15 F sub­
cooling). Optimum charge activates the subcooling
circuit, resulting in higher system capacity at slightly
higher head pressure and corresponding condensing
temperature. Liquid refrigerant leaves the system sub­
cooled to a stable condition to allow greater length of
refrigerant run or lift.
Otherwise, use minimum charge which gives higher heaf
rejection, since entire surface of condenser and sub­
cooling circuit is used for condensing only. Minimum
charge ratings, however, do not represent greatest po­
tential system capacity. They are comparable to com­
petitive ratings without subcooling.
b. List the refrigerant, total heat rejection (THR), suction
and discharge temperatures as determined from com­
pressor data.
2. Determine condensing temperature (saturated discharge
temperature minus discharge line loss).
3. Determine temperature difference (condensing tempera­
ture minus entering air temp).
4. Enter Condenser Ratings table (minimum or optimum
charge as determined in Step 1) at selected refrigerant
and established temperature difference. Read across
to total heat rejection equal to or greater than required.
Interpolate if necessary. Read unit size.
Example (Optimum Charge)
1. Given:
R-22, Optimum Charge
THR (including subcooling).......................................................... 29.4 Tons
Saturated Disch Temp................................................................................ 123.8 F
Saturated Suction Temp.................................................................................. 40 F
Entering Air Temp............................................................................................95 F
Disch Line Loss................................................................................................. 2 F
2. CondTemp^ 123.8F-2F= 121.8F
3. TD = 121.8F-95F- 26.8 F
4. Interpolate in Condenser Ratings table (optimum charge)
and obtain capacity of 09DC028 as 30,0 tons and 09DC024
as 23.6 tons. Select the 09DC028.
Example (Minimum Charge)
1. Given:
R-12, Minimum Charge
THR . . ■.................................................................................... 15.0 Tons
Saturated Disch Temp...................................................................................122 F
Saturated Suction Temp..................................................................................40 F
Entering Air Temp........................................................................................... 95 F
Disch Line Loss ............................................................................................ 2 F
2. Cond Temp = 122 F-2 F - 120 F
3. TD= 120 F-95 F-25 F
4. Enter Condenser Ratings table (minimum charge) and
select 09DC016 with 15,2 tons THR. (Note that with
optimum charge this unit has THR of 14.8 tons which
does not meet specifications).
*See Carrier System Design Manual.